Abstract It has been proposed that cultivating calm will increase altruism and decrease parochialism, where altruism is defined as self-sacrifice in support of others, regardless of group affiliation or identity, and parochialism is defined as prosocial self-sacrifice restricted to fellow members of a group. Such could be the case with a calming meditation practice. An alternate hypothesis, coming from the study of ritual, proposes that shared practices lead to bonding, increasing parochialism, but not altruism generally. These contradictory hypotheses of the potential effects of shared cultural practices of calming meditation were explored via a formal behavioral experiment using a simple treatment and control format with a short, facilitated breath awareness practice known to produce calm. Altruism and parochialism were measured through anonymous play in Public Goods games performed with both in-group and out-group individuals. The sum of contributions of the two plays gave a measure of altruism, while the difference between the two gave a measure of parochialism. The analysis of the results using Bayesian AICc model comparison methods supports the first hypothesis that calming practices reduces parochialism and increases altruism. The hypothesis of intentional shared practice as parochialism inducing was not supported by the results in this case of a shared calming practice.